boom. [ male announcer ] pillsbury crescents. make the holidays pop. ♪ ♪ ♪ ♪ [ male announcer ] when you feel good, no one is immune. emergen-c has more vitamin c than 10 oranges plus other antioxidants and electrolytes to help you come down with a serious case of healthy. emergen-c. making healthy contagious. >>> time for morning rounds our look at the top medical news of the week. joining us are cbs news chief medical correspondent, dr. john and cbs news contributor dr. holly phillips. >>> the center force disease control says the rate of twin birth is up 76% over three decades, in many cases it's a result of fertility treatments. now some specialists involved in so-called miracle babies are proposing new guidelines. they recommend just one baby at a time. >> john, why are the multiple births a problem here? and what are they recommending? >> well the problem is when you have multiple births you have increased risk of dangerous side effects, complications to the mother and the child. with twins, five times increased ris